Process of electrodepositing chromium



June 16,- 1931. v w. s. BOHLMAN 7 1,309,826 I I PROCESS OF ELECTRODEPOSITING CHROMIUM Filed Sept. 6. 1927 Patented June 16, 1931 UNITED s'ra'ras WALTER S. BOHLMAN,

CORPORATION OF AMERICA,

] ATLANTIC CITY,

OF NEW YORK,

NEW JERSEY, ASSIGNOR '1'0 GHROKIUI N. Y., A CORPORATION 01 DELAWARE PROCESS OF ELECTRODEPOSITING OHROMIUE Application filed September a,

This invention relates to chromium lating, and aims to provide improvements t ere- The resent invention provides a method of 5 chromium platin particularly adapted for efiecting such p'atmg on areas which by the ordmary methods present unusual difliculties. It is articularly adapted for plating on the un 'erside of articles, in recesses, pockets, corners and the like, and on the inside of pipes, and particularly pipe having irre lar axial shapes.

G romium plating is accompamed by a considerable evolution of hydrogen gas in the area in which the metal is deposited, and where this gas accumulates or is trapped, as for example on the under side of articles, in ockets and recesses, and in pipe, plating may e interfered with or prevented following the 2 ordinary methods of plating. j

According to the resent invention, I ap ply the solution to ted areas at a time, in the form 'ofa stream, with lateral contact of the solution" with the atmosphere near the zone of plating insu'ch manner that, when the current is acting the gas generated in the plated area'has lateral egressto the atmosphere.

Several modes of procedure in carrying out the process are illustrated in the accompanyin drawings, wherein:

igure 1 illustrates a mode of procedure in (plating the inner sides of a large vessel, an 85 Fig. 2 illustrates a mode of procedure in plating the inside of a pipe having a bend therein. Y

Referring to Fig. 1, a platingsolution' is forced or projected in suitable manner, as from a metallic nozzle 10, against the portion 12 of a surface to be plated, such surface bein here shown as the inner wall at the under! 1 of streams and "for the escape against which si e of a large vessel 13. The metallic nozzle 10 is conveniently covered with a rubber or other-insulatin covering 14 to protect the operator from s ock and to avoid short circuits being formed between the nozzle and metallic objects with which it may come into contact. The stream of solution is conveniently forced through the nozzle 10 by pump catalyst, such for example and over 1927. Serial No. 217,597.

1?, a suitable hose connection 17 being arovlded, between the nozzle and the pump. he pump ma draw the solution from any suitable supply. There is here shown a pan 19 beneath the nozzle for catchin the solution falling back from the surface 0% and this solution may flow off from the pan to any suitable receptacle through the pipe 21. The vessel 13 is made cathode by connecting it with the negative side of a source of current, as indicated at 25,and the nozzle 10 is made anode by connec 'ing it with the positive side of the source of current supply, as indicated at 27.

The nozzle is moved to successive portions of the surface of the article to be plated, and the plating of a large area effected successively in this way..

The solution used is trated chromic acid so ution, containing a as disclosed in the lf'atent No. 1,581,188, granted April 20,

the vessel 13,

referably a concenv The electric current makes contact with the solution through the metallic nozzle 10, and flows through the stream of solution to the surface of the cathode article against which the stream strikes. The curren effects the reduction of chromic acid an the deposit of the chromium, and also effects the release of'hydrogen at the cathode. As the stream of solution is in contact with the atmosphere, the hydrogen gas has a ready means of egress from the lating zone, and hence even when plating is one on the under side of articles, in recesses, corners, pockets 'and the like, it has aready means of egress from the stream to the atmosphere at the side of the stream, and thus avoids a condition where the hydrogen would accumulate and thereby retard or prevent the plating.

The stream may be divided into a plurality thereby provide air spaces of gas throughout the area the plurality of streams as a w ole is directed.

'With this method of platin it is diflicult to estimate the area covered y the stream which plating-is taking place. The

current density must therefore in most cases i nozzle placed four'inches from a surface, I

be obtained by experiment I may indicate that I use considerably higher voltages than used in ordinary chromium plating, ordinary connecting the nozzle to a 100to 120-volt circuit. Using a one-sixteenth inch obtain plating with an' ammeter reading of one-half ampere.

The proper current density for plating is readil obtained by moving the nozzle closer to or urther away from the cathode surface, until the desired plateis observed, and the current density during plating is regulated in like manner.

It is known that there is a co-relation between quantity of catalyst in the solution, current density and temperature, and with a known solution as regards concentratlon of chromic acid and catalyst content, an adjustment of the temperature is effected by having regard to the temperature of the article bein plated, the heating effect of the current, an the temperature of the solution supplied to the nozzle. 5 If the article is large and at room temperature or below, a proper temrature in the zone of plating is effected by iiiivin the temperature of the solution consideraily higher than the estimated temperature at WhICh it is desired to efi'ect plating -say for exam 1e a plating temperature of fect of the current is verygreat, and ordi- -.narily the heating of the stream is obtained not stored or accumulated from the heatin effect of the current the solution supplieg to the nozzle be ordinarily unheated. The supplying of e nozzle with cold or unheated solution has the advanta e that higher current densities can be used than are ordinarily used in tank platin The heat generate .in the stream of sofution between the nozzle and cathode is in a body of solution in the zone of platin but passes off with the solution falling bac from the cathode, and therefore the stream can carry a higher current density than could be used in plating a surface of equal areaimmersed in a plating solution in .a tank.

A second mode of practising the invention is illustrated in Big. 2. The article to be plated is a pi 30, and is shown as having a right-an e bend therein. With such a pipe it would difiicult to-fit an inside anode, and also diflicult to prevent an objectionable accumulation of hydrogen. According to my process, a pipe 32 having a suitable nozzle 34 on oneend is inserted mto the pi e30, and a stream of liquid projected latera y against the inner side of the ilpe 30, the pi 32 and nozzle 3*; being move engthwise 0 the Pipe e solution projected from 30 to coat successive areas. The pipe 82 may be mafie-lflesxlilble to follow tgethcontour 3f lrregu r a p1 an e ipe 2 and nozzl 84 m 2; be uierted first iiito the lated at one end and then into the pipe to plated at the other end. Suitable insulated sugports 36, 37 for the pipe 32 may be provid if desired.

The nozzle 34 is convenientl of a nature to plroject a disk-shaped or radiating stream, as ere shown. Pi 32 is made anode,- as by connecting a condiictor 38 thereto, and the pipe 30 is made cathode as b connecting a conductor 40 thereto, the conductors 38 and 40 being connected respectively to the plus and minus side of a source of current. Plating solution is continuously supplied to the pipe 32 during plating, in any suitable manner.

The disk-shaped stream of plating solution communicates with the atmosphere on either side, so that there is a ready means of egress of the hydrogen evolved during the process, from the zone of lating, and in this manner accumulation of hydrogen which would interfere with the lating, 1s avoided.

The invention is applicable to other platin solutions wherein considerable volumes 0% gas are released during plating in the cathe area.

The invention may be practiced in many other modes of procedure than those herein specifically illustrated and described.

at is claimed is 1. A method of electrodepositing chromium comprising projecting a ChIOlIlIC acidacid radical platin solution against a sur face in the form of a free jet, and passing a current through said jet largely in excess of the current required for normal depositions on an area corresponding to the cross-sectional area of saidjet. v

2. A'method according to claim 1, wherein said solution is supplied to said jet at normal room temperature.

3. A method according to claim I wherein a plating solution of a chromium type is pro-' ted with suflicient force against a cathode surface that large quantities of gas disengaged at the cathode surface are displaced whereby metal can be deposited from said solution onto said cathode Surfaces.

. In. witness whereof, I have hereunto signed my name.

.WALTER s. BOHLMAN. 

